Among typical optical devices, for example, a solid-state image device made up of a solid-state image element uses an optical low-pass filter which interrupts unnecessary high frequency components and includes an optical crystal plate. In order to reduce the size and weight of a device, an optical low-pass filter using a diffraction grating is used (for example, see Japanese Patent Laid-Open No. 53-119063).
Such an optical low-pass filter has to be precisely positioned on the imaging surface of a solid-state image element. However, it is not always easy to precisely perform positioning on the order of μm. Thus, it is not possible to sufficiently prevent the occurrence of a diffraction grating image on a screen and the productivity is hard to increase. As a solution to this problem, as shown in FIG. 10, it has been proposed that a solid-state image element 1 and an optical low-pass filter 2 are fixed via a gap regulator 3 to regulate a gap between the solid-state image element 1 and the optical low-pass filter 2, so that precise positioning is performed on the order of μm (for example, see Japanese Patent Laid-Open No. 6-334159).
On the other hand, as to a package structure of a solid-state image device, a directly bonded structure has been proposed (for example, see Japanese Patent Laid-Open No. 3-151666) instead of a hollow structure of the prior art (see FIG. 10). In the directly bonded structure, a translucent plate is directly bonded to the light receiving part (or the light emitting part) of a semiconductor substrate with a translucent adhesive. An advantage of the directly bonded structure is that the sensitivity of the solid-state image device can be increased by equalizing the refractive indexes of the translucent plate, the translucent adhesive, and the flat film of the semiconductor substrate. The directly bonded structure can easily reduce the size and thickness of a package and also prevent process dust and mobile dust from entering the light receiving part.
Thus, it is considered that in the configuration of an optical device such as a solid-state image device (light receiving device) and an LED device (light emitting device), the directly bonded structure can be used in which the translucent plate is directly bonded on one of the light receiving part and the light emitting part with the translucent adhesive and the gap regulator can be used to precisely position one of the light receiving part and the light emitting part and the translucent plate or to stop the flow of the translucent adhesive.
However, for example, in the configuration of a solid-state image device shown in FIG. 11, when a translucent plate 2 such as an optical low-pass filter is placed, a translucent adhesive 5 applied on a light receiving part 12a of a semiconductor substrate 11 by a single-point application method is largely pressed out of linearly convex portions 3, particularly out of the center of the convex portions 3 as shown in FIG. 12A, so that the translucent adhesive 5 adheres to electrodes 13 disposed on the ends of the semiconductor substrate 11. When the translucent adhesive 5 is applied to two points on the light receiving part 12a as shown in FIG. 12B, it is possible to prevent the translucent adhesive 5 from being pressed out of the convex portions 3. However, air is trapped between the translucent adhesive 5 on the two points and causes internal voids. As a solution to such voids, an underfill method is effective, that is, it is effective to flow the translucent adhesive 5 by using a capillary phenomenon while setting the translucent plate 2 on the convex portions 3. However, as shown in FIG. 13, the translucent adhesive 5 flows out of the translucent plate 2 (and the convex portions 3).